You may like to know my encounter yesterday and take precautions promptly.
I anchored my boat some 20 feet from a beach. Half an hour later, a pleasure craft 40 ft came and moored about 20 feet away from my boat despite that everywhere was almost empty. I was on shore and the craft driver took some of the passengers to shore on an inflatable. I was concerned on how close this craft was to my small speed boat. What surprised me more was, without the driver, someone on board moved the anchore line from the bow to the middle of the boat. I said "hell, there was going to be collision" and swam out to warn that guy. As soon as I was within 10 ft from my boat, the craft began to swing into my boat and a lady on board jumped onto the driver seat and tried to steer the boat away. I didnt know what she did. I had to quickly swum away for safety (only 2 ft apart)and abandon my boat. The craft almost hit my outboard and the driver on shore shouted and gave instructions to the lady to let go the anchor line and do nothing on the motor. The craft slowly drifted back and I quickly swam to my boat and drove it away to a safe spot. The craft was only 10 feet from shore and it was lucky that it did not go aground.
Next time you see some stupid guys doing the same thing near to your boat. My advice is dont wait and immediately drive away. When you do this, make sure that you are safe. Dont assume all boat goers are sensible.